Abstract

2'(3')-O-Phosphonylmethylribonucleosides II, III were prepared by intramolecular cyclisation of ribonucleoside 2'(3')-chloromethanephosphonates I in alkali. Treatment of the phosphonylmethyl derivatives with dicyclohexylcarbodiimide afforded cyclic six-membered estersVI, VII which are stable in acid and easily hydrolyze in alkali. Ribonucleases A, T1, T2, U2 and spleen cPDase do not split the cyclic phosphonate ester linkage of these analogues of ribonucleoside 2',3'-cyclic phosphonates.